JPH114448A - Image signal transmitter and image signal transmission method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent the production of noise by transmitting a 2nd image signal in succession to a 1st image signal, when a GOP at the head of the 2nd image signal is of an open-type, based on a discrimination result of a discrimination means. SOLUTION: A 2nd image stream is fed to a control section 12, at which whether or not a head GOP is a closed GOP is discriminated. In the case that the head GOP is a closed GOP, a last GOP of the 1st image stream is sent to the outside via a switching terminal (a) of switches 14A, 15, the switch 15 is immediately thrown into a position of a switching terminal (b), and the 2nd image stream is outputted in succession to the 1st image stream. In the case that the head GOP is the open GOP, after the last GOP of the 1st image stream has been to the outside via the switch 15, the switch 14B is immediately switched. Data outputted from an MB code conversion section 18B are fed to the switching terminal (b) of the switch 14B and then outputted to a switching terminal (b) of the switch 15.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

[Table of Contents] The present invention will be described in the following order.

BACKGROUND OF THE INVENTION Prior Art (FIG. 6) Problems to be Solved by the Invention (FIGS. 7A to 9)
(D) Means for Solving the Problems Embodiment of the Invention (1) Principle (FIGS. 1A to 3) (2) Configuration of Television Broadcasting System According to Embodiment (FIG. 4) (3) Image Stream Switching Processing Procedure (FIG. 5) (4) Operation and Effect of Embodiment (5) Other Embodiment Effects of the Invention

[0003]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an image signal transmitting apparatus and an image signal transmitting method, and more particularly to a method for transmitting a video signal to an MPEG signal.
(Moving Picture Experts Group) Image signal compressed and coded according to the standard (hereinafter referred to as an image stream)
Is suitably applied to an image signal transmitting apparatus and an image signal transmitting method for switching and transmitting at an arbitrary timing in GOP (Group of Pictures) units.

[0004]

2. Description of the Related Art In recent years, there is a television broadcasting system as shown in FIG. In the television broadcasting system 1 having such a configuration, the video signal S1 such as a program or CM (commercial) is transmitted by the MPEG
The image streams encoded by the encoder 3 are sequentially stored in the data storage unit 4. At the time of broadcasting these programs and CMs, the corresponding image streams are sequentially read from the data storage unit 4 and are read out from the temporary data storage unit 5.
And via the switch 6 to the receiving side.

In the image signal transmitting apparatus 2, when a program or CM is switched, an image stream of the program or CM is read from the data storage section 4 before the end of the previous program or CM, and a part of the beginning is read. To the temporary data storage 7
To store. When the image stream is switched, the switch 6 is switched after the end of the last GOP of the program or CM image stream before being output from the temporary data storage unit 5, and the program or CM image stream following from the temporary data storage unit 7 is switched. And sends it out to the receiving side via the switch 6.

[0006] Thus, the television broadcasting system 1
Then, on the receiving side, the supplied image stream is sequentially decoded by the MPEG decoder 8, so that a television broadcast which is sequentially displayed while a program or CM is switched can be viewed.

[0007]

By the way, in the image compression coding system based on the MPEG standard, an intra-frame coded image (I-picture (I-picture)) in which at least the first one of each GOP is coded independently of other frames. intra coded pict
ure)) and the rest are predictively coded based on other frames, and are inter-frame predictively coded images (forward coded pictures (P pictures) or bidirectionally coded pictures (B pictures). pi
cture)).

In this case, in such an image compression coding system, the sequence of original images as shown in FIG. 7A is converted into an image stream having a sequence of coded images as shown in FIG. Then, the original image is displayed by being returned to the original image sequence shown in FIG. 7C by the decoding process.

By the way, in such an image compression coding system,
Normally, as shown in FIG. 8A, the first B picture group of a GOP is composed of the first I picture of the GOP and the preceding GOP.
Are inter-frame predictive coded based on the last I-picture or P-picture.

For this reason, in the television broadcasting system 1 described above, the first image stream in which the coded images are arranged as shown in FIG.
When a second image stream having a sequence of encoded images as shown in (B) is switched and transmitted as shown in FIG. 9 (C),
The first B-picture group of the second image stream is decoded by the MPEG decoder 8 on the receiving side based on the I-picture or the P-picture of the uncorrelated first picture stream as shown in FIG. 9D. However, there is a problem in that the reproduced image of the B-picture group becomes a high-noise image without quality.

In this case, in such an image compression coding system,
As shown in FIG. 8B, there is a method of converting a GOP into a closed GOP that is encoded independently of the preceding GOP. However, this method is effective when the switching position is already known from the beginning, but when it is desired to edit freely after encoding, many GOPs are previously closed GOPs.
There is a problem that it is necessary to use an OP and the image quality is deteriorated.

Further, in such an image compression coding system, a closed GOP is set by setting a broken link flag.
Although there is a method of indicating to the decoder that the image streams that are not connected by editing are connected, and preventing the decoder from reproducing the first B-picture group, this method depends on the correspondence of the decoder.

The present invention has been made in consideration of the above points, and the first and second image signals can be output at arbitrary timing in GOP units without deteriorating the image quality and without generating noise at the corners. An image signal transmitting apparatus and an image signal transmitting method which can be switched and transmitted are proposed.

[0014]

According to the present invention, in order to solve the above-mentioned problems, a plurality of coded image groups leading an intra-frame coded image are represented by a group of pictures (GOP).
In an image signal transmitting apparatus that switches and transmits the first and second image signals composed of one or a plurality of GOPs in GOP units, the first GOP of the second image signal
Determining whether the type is a closed type coded independently of the preceding GOP or an open type coded depending on the preceding GOP, and a first type of the second image signal. An image replacement unit that replaces the inter-frame prediction encoded image group with an inter-frame prediction encoding group based only on the first intra-frame encoded image of the second image signal; And transmitting means for transmitting, after the first image signal, the second image signal replaced by the image replacing means when the first GOP of the image signal is open type.

In the present invention, a plurality of coded image groups leading the intra-frame coded image are defined as a GOP (group of pictures), and the first and second image signals composed of one or a plurality of GOPs are provided. Is switched in GOP units and transmitted, the first GOP of the second image signal is a closed type encoded independently of the preceding GOP or encoded depending on the preceding GOP. A first step of determining whether the type is an open type, and a first GOP of the second image signal.
Is an open type, the first inter-frame predictive coded image group of the second image signal is converted into the inter-frame predictive coded group based only on the first intra-frame coded image of the second image signal. A second step to be replaced and a third step to transmit the replaced second image signal following the first image signal are provided.

As a result, when the image signal output from the image signal transmitting apparatus is reproduced, the inter-frame prediction coded image group to be transmitted in place of the first inter-frame prediction coding group of the second image signal is Since the decoding is performed only on the basis of the first intra-coded image of the second image signal, the same image continues between the image based on the first image signal and the image based on the second image signal. Although the resulting still image is displayed for a moment, no noise is generated when the first and second image signals are switched.

[0017]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below in detail with reference to the drawings.

(1) Principle The first image stream ST ₁ shown in FIG.
Second and an image stream ST ₂ shown in (B), when after the first of the last GOP of the image stream ST ₁ so as to switch to the second image stream ST ₂ outputs, the second image stream ST2 is converted to a _second image stream S uncorrelated with the _first image stream ST1.
Consider the case of replacing with T ₂ ′ (FIG. 1C).

As a premise, the MPEG standard (for example, M
In the image compression coding system based on the PEG1 standard, each picture is composed of a plurality of slices each consisting of a minimum unit in a series of data strings having a start code, and each slice is a plurality of macroblocks (MBs). It is configured as a belt.

Each of these macroblocks (FIG. 2A)
As shown in FIG. 2B, MBSTUFF (Macrob
lock Stuffing), MBESC (Macroblock Escape)
), MBAI (Macroblock Address Increment), M
BTYPE (Macroblock Type), QS (Quantizer Sc
ale), MHF (Motion Horizontal Forward), MV
F (Motion Vertical Forward), MHB (Motion Hor)
izontal Backward), MVB (Motion Vertical Backwa)
rd), a CBP (Coded Block Pattern), a block layer (conversion coefficient itself), and fixed-length or variable-length data are sequentially arranged in a line, and are terminated by an EOMB (End of Macroblock).

MBSTUFF is data indicating a dummy code when the code amount is insufficient, and MBESC is data of MB33.
This is data corresponding to the skips. Also MBAI
Is data having a variable length code (VLC: Variable Length Code) for skipping MBs that do not require information.

Further, MBTYPE (hereinafter referred to as MB type) is data having a variable length code (VLC: Variable Length Code) indicating a classification of a processing method of a macro block, and corresponds to I, P and B pictures. Each VLC is set.

FIG. 3 shows a classification table of the MB type for the B picture. In this table, the MB type VLC in the B picture is represented by MBQUANT (whether or not the quantization step is updated), MB forward prediction, MB backward prediction, and MB pattern (any of coding required or unnecessary, that is, DCT). Binarization is performed depending on whether or not a coefficient code is added or not and whether or not MB intra (intra-frame predictive coding) is performed, and the data is classified into 11 types according to these results.

First, a second image stream ST ₂ (FIG. 1)
For the first B picture group of (B)), the type of each macro block of B pictures B _B0 and B _B1 constituting the B picture group is converted into a predetermined code.

Thus, V-type VLC of B picture
The by transcoding to "010" (hatched portion in FIG. 3), the head of the B-picture group in the second image stream ST _2, the leading B-picture B _B0 and B _B1 respectively I picture B _I2 only It can be replaced with B pictures C _B0 and C _B1 which are backward prediction and do not require encoding (FIG. 1 (C)).

Thereafter, the second image stream S
T ₂ ′ is switched and output after the last GOP of the _first image stream ST ₁ . As a result, the image stream ST as shown in FIG.
₃ is obtained, a data sequence having an image arrangement as shown in FIG. 1 (E) is obtained. Thus, as a reproduced image, the head of the _second image stream ST ₂ ′ follows the image based on the first image stream ST _1. Is displayed for a moment, and then the second image stream S
An image based on the beginning of T ₂ ′ is displayed.

[0027] In this case the second image stream ST ₂ 'the top of the B picture C _B0 and C _B1 of, the second image stream ST _2' is decoded by the backward prediction of only the first I picture B _I2 of Therefore, the first and second image streams S
At the beginning of the joint between T ₁ and ST ₂ ′, three identical images (B-pictures C _B0 and C _B1 and I-picture B _I2 ) are momentarily displayed as a continuous still image, but no noise is generated.

(2) Configuration of Television Broadcasting System According to Embodiment FIG. 4 in which parts corresponding to those in FIG.
1 shows a television broadcasting system 10 according to an embodiment, in which a control unit 12 of an image signal transmitting apparatus 11 has a data storage unit 4 and a temporary data storage unit 13 based on a command given from a higher-level application (not shown).
By controlling the driving of the switches A and 13B and the switches 14A to 15 to desired states, the above-described switching process can be performed.

In practice, the television broadcasting system 10
In the case of (1), the data storage unit 4 of the image signal transmitting device 11 stores the image stream (the first image stream ST in FIG.
₁ ), and reads them out temporarily.
3A, the switching end a of the switch 14A and the switching end a of the switch 15 are sequentially transmitted to the MPEG decoder 8 on the receiving side.

On the other hand, when the program or CM is switched, before the end of the previous program or CM, an image stream (the second stream in FIG. and image stream ST ₂₎ the data storage unit 4
From the temporary data storage unit 13B
Is accumulated in

At this time, the second image stream ST ₂ is also supplied to the control unit 12, and the control unit 12 sets the first GOP of the second image stream ST _{2 as} the preceding GOP.
It is determined whether the type is a closed type coded independently (ie, a closed GOP) or not.

When the image stream is switched, the first GOP of the _second image stream ST2 is closed GO.
When been made in P, after the first of the last GOP of the image stream ST ₁ is One Owa sent to the outside sequentially through the switching terminal a of the switching terminal a and switch 15 of the switch 14A, immediately switch 14B is switched The switch 15 is switched to the switching end b while the switch is switched to the terminal a, and thus the second image stream ST ₂ is output from the switch 15 following the _first image stream ST ₁ .

On the other hand, the second image stream ST ₂
Is the open GOP, the last GOP of the _first image stream ST1 is the switch 1
The switch 14B is immediately switched to the switching terminal b after the transmission to the outside through the switch 5 is completed.

[0034] (a image stream ST ₂ second in FIG. 1 (B)) In this case the image stream that is stored in the temporary data storage section 13B is supplied to the picture type and the number detecting unit 17B of the picture group substitution unit 16B , The picture numbers (TR: Temporal Reference) and the picture type (PCT: Picture Coding Type) of the coded pictures (B pictures) B _BO and B _B1 of the second picture stream ST ₂ are detected, respectively.

The B pictures B _BO and B _B1 detected thereafter
Is the MB (macro block) code conversion unit 18B
And the type of each macro block of the B pictures B _BO and B _B1 is converted into a predetermined code. As a result, B pictures B _BO and B _B1 are backward predictions of only the first I picture B _I2 and B pictures C _B0 which do not require encoding.
And _CB1 .

[0036] The switching terminal b of the switch 14B this manner, is supplied with the data of MB B outputted from the code conversion unit 18B picture C _B0 and C _B1, which switching terminal b of the switch 15 from the switch 14B Is output to

Thereafter, when the data of the coded images (I picture B _{I2 and} B pictures C _B0 and C _B1 ) for the first three pictures of the second picture stream ST ₂ ′ are output from the switch 14B, the switch concerned 14B is immediately switched to the switching terminal a, and at this timing, the temporary data storage 1
Following the data of three encoded pictures of 3B (I picture B _{I2 and} B pictures C _B0 and C _B1 ), a second picture stream ST ₂ ′ is outputted from the switch 14B to the switching end b of the switch 15. .

Thus, the television broadcasting system 1
In 0, it has been made from the image signal transmission apparatus 11 so as to be able to deliver the image stream ST ₃ as shown in FIG. 1 (D).

[0039] Note that when further switching the image stream ST ₃ to the image stream (not shown) of the next program, switches the switch 15 to the switching terminal a, in accordance with switch 14A to the type of the head of the GOP of the image stream By switching to the switching end a or b, the temporary data storage unit 13A and the picture group replacement unit 16 are switched.
The same processing as the above-described image replacement method can be performed on the A side.

(3) Image Stream Switching Processing Procedure A series of operations in the image signal processing device 11 described above are performed by the control unit 12. In practice, the control unit 12 performs the image stream switching processing procedure RT shown in FIG.
Accordingly, when the command C1 is given from the upper application to switch the image stream, this image stream switching processing procedure RT is started in step SP1, and in the next step SP2, the data storage section 4 and the following temporary data are stored. each causes read the first image stream ST ₁ sends out a control signal in the storage unit 13B, the first image stream ST ₁ by switching the switch 14A and switch 15 in each switching terminal a to the MPEG decoder 8 Send out.

[0041] Subsequently, the control unit 12 sends at step SP3, this by to read the data storage unit the second image stream ST ₂ by sending a control signal to 4 in the temporary data storage section 13B and the control unit 12 together it is, by a checking of the second near the beginning of the image stream ST ₂ obtained, find a storage area CG (Closed GOP) flag. When detecting the storage area of the CG flag, the control unit 12 proceeds to step SP4 and determines whether or not the flag is stored in the storage area (that is, whether the first GOP of the _second image stream ST2 is a closed GOP). No) is determined.

When the control unit 12 obtains a positive result in step SP4, the control unit 12 proceeds to step SP5 to switch 1.
After switching the 4B to switching terminal a, the process proceeds to step SP6, from the temporary data storage unit 13A based on the first timing signal provided to each end of each GOP of the image stream ST _1, first image stream ST _The GOP closest to the switching timing of ₁ is the temporary data storage unit 13.
While starting the second reading of the image stream ST ₂ in the temporary data storage section 13B at a timing One Owa output from A, by switching the switch 15 to the switching terminal b, and the second image stream ST ₂ first Following the image stream ST ₁ is output from the switch 15.
Thereafter, the flow advances to step SP7 to end the image stream switching processing procedure RT.

On the other hand, the control unit 12 executes the step SP
If a negative result is obtained in step 4, the process proceeds to step SP8 to switch the switch 14B to the switching end b, and then proceeds to step SP9, based on the timing signal supplied from the temporary data storage unit 13A. an image stream ST switch 15 closest GOP to _one switching timing is at the timing at which one Owa outputted from the temporary data storage section 13A by switching to the switching terminal b of the second image stream ST ₂ the picture group substituted portion 16B To the picture type and number conversion unit 17B.

Subsequently, in step SP10, the control unit 1
The 2, after the picture number and the picture type of the second image stream ST ₂ of B in picture type and the number conversion unit 17B of the picture group substituted portion 16B picture B _BO and B _B1 were respectively detected, proceeds to step SP11 Based on the detection result, the MB code conversion unit 18B converts the type of each of the macro blocks of the B pictures B _BO and B _B1 into a predetermined code, so that the B pictures B _BO and B
_B1 is replaced with B pictures C _B0 and C _B1 which are backward predictions of only the first I picture B _I2 and do not require encoding.

Thereafter, the control unit 12 sends the data of the B pictures C _B0 and C _B1 to the switch 15 and then switches the switch 1.
4B is switched to the switching terminal a, and the data of the _B pictures C _B0 and C _B1 is followed by the second image stream ST ₂ ′.
Is transmitted from the partial data storage unit 13B to the MPEG decoder 8 via the switch 14B and the following 15. Thereafter, the flow advances to step SP7 to end the image stream switching processing procedure RT.

(4) Operation and Effect of Embodiment In the above configuration, the television broadcasting system 1
0, when switching the image stream to be sent to the MPEG decoder on the receiving side via the switch 15 from the first image stream ST ₁ to the second image stream ST ₂ , the second image stream ST
₂ of the first GOP is previously detects whether the closed GOP, leave to output a second image stream ST ₂ to the first image stream ST ₁ when been filed in the closed GOP.

On the other hand, in the image signal transmitting device 11,
If the first GOP of the second image stream ST ₂ is an open GOP, the B of the _second image stream ST ₂
By converting the type of each macro block of the picture B _BO and B _B1 into a predetermined code, the corresponding B picture B _BO
And B _B1 are replaced by B pictures C _B0 and C _B1 which are backward predictions of only the first I picture B _I2 and do not require encoding, and are followed by B pictures of the second image stream ST ₂ .
It outputs the data of the coded images of the pictures B _BO and B _{B1 and} thereafter.

As a result, the television broadcasting system 1
In the case of 0, the image stream ST ₃ as shown in FIG. At this time, of the image streams ST ₃ , the second image stream ST ₂
B picture groups C _B0 and C following the first I picture B _I2 of
As described above, _B1 is a backward prediction of only I-picture B _I2 and is replaced so that encoding is unnecessary. Therefore, at the time of decoding, only B- _I2 at the head of the _second image stream ST2 is replaced. to be decoded on the basis of the first image stream ST from the reproduced video based on ₁ second image stream ST at the time of switching of ₂ to based reproduced video three same image (B picture C _B0 and C _B1 and I-picture B _I2 )
Are displayed for a moment as a continuous still image, but no noise is generated.

According to the above configuration, when switching from the _first image stream ST ₁ to the second image stream ST ₂ , the GO of the first GOP of the _second image stream ST ₂ is changed.
Detecting a P type, if the GOP has been made in an open GOP is the convert the type of each macroblock of the second B-picture of the video stream ST ₂ B _BO and B _B1 a predetermined code B picture B _BO and B _B1 are the backward prediction of only the first I-picture B _I2 and B which does not need to be encoded.
The pictures are respectively replaced by pictures C _B0 and C _B1 , followed by pictures B _BO and B B of the _second image stream ST _2.
By which is adapted to output the data after encoded image _B1, noise occurs in the switched during the playback video based on image stream ST ₂ reproduced video and the second based on the first image stream ST ₁ And an image signal transmitting apparatus capable of switching the first and second image streams at an arbitrary position in a GOP unit without causing image quality deterioration and without generating noise at a joint. realizable.

[0050] (5) Other In the embodiment noted embodiments of the above-described, the GOP head of GOP of the second image stream ST ₂ is, independently of the preceding GOP to a closed type or preceding encoded A case has been described in which the determination unit that determines which of the open types is coded depending on is used together with the control unit 12 that controls the entire image signal transmission device 11, but the present invention is not limited to this. However, the present invention is not limited thereto, and the determination unit may be configured separately from a control unit that controls the entire image signal transmission device 11.

[0051] Further in the above embodiment, the second first interframe predictive coding images of an image stream ST ₂ (i.e. B-picture group), and the second image stream ST ₂ in the first frame As shown in FIG. 4, a temporary data storage unit 13A (13B) and a picture group replacement unit 16A (16) replace an image replacement unit that replaces with an inter-frame prediction coding group based only on a coded image (that is, an I-picture).
B), the present invention is not limited to this, but the point is that the second image stream ST ₂
Of the first inter-frame predictive coded picture group, if it is possible to replace the inter-frame predictive coding group based only on the second of the first frame in the coded image of the image stream ST _2, a configuration of the image replacement means , And various other configurations can be applied.

Further, in the above embodiment, the second
Of the first inter-frame prediction coding image group of the image stream ST _2, a method of replacing the inter-frame predictive coding group based only on the second of the first frame in the coded image of the image stream ST _2, the second Image stream ST
The type of each macroblock of the _second B-picture B _BO and B _B1 using the method of converting the predetermined code, the B-picture backward prediction a and the sign of the B _BO and B _B1 only the first I picture B _I2 Although the case where the B pictures C _B0 and C _B1 which do not need to be converted are respectively replaced with each other has been described, the present invention is not limited to this, and the first inter-frame prediction coded image group of the second image stream ST ₂ may be replaced by , if it is possible to replace the inter-frame predictive coding group based only on the second of the first frame in the coded image of the image stream ST _2, as an image replacement method may be applied to various methods.

Further, in the above embodiment, the second
The head of the GOP image stream ST ₂ is when been made in an open type, picture group substituted portion 16A (16B)
The sending means for sending a second image stream ST ₂ which are replaced Te Niyotsu followed the first image stream ST _1, the control unit 12 and switch 14A (14B) and 1
It has dealt with the case of construction in 5, the present invention is not limited to this, short, when the head of the GOP of the second image stream ST ₂ has been made in an open type, picture group substituted portion 16A ( a second image stream ST ₂ the first image stream ST has been replaced Te 16B) Niyotsu
_As long as the transmission can be carried out after the _one , various other configurations can be applied as the configuration of the transmission means.

[0054]

As described above, according to the present invention, a plurality of encoded image groups leading an intra-frame encoded image are represented by a GOP.
(Group of Pictures) as one or more GOs
In an image signal transmitting apparatus that switches and transmits the first and second image signals composed of P in GOP units,
Determining means for determining whether the first GOP of the image signal of the first GOP is a closed type coded independently of the preceding GOP or an open type coded depending on the preceding GOP; Image replacement means for replacing the first inter-frame prediction coded image group of the second image signal with an inter-frame prediction coded group based only on the first intra-frame coded image of the second image signal; Based on the result, when the first GOP of the second image signal is of the open type, the transmitting means for transmitting the second image signal replaced by the image replacing means following the first image signal. With this arrangement, the first and second image signals can be switched at arbitrary timings in GOP units without causing image quality deterioration and without generating noise at the corners. It is possible to realize an image signal transmission apparatus capable.

Further, according to the present invention, a plurality of coded image groups leading an intra-frame coded image are defined as a GOP (group of pictures), and the first and second images composed of one or more GOPs In an image signal transmission method for switching and transmitting a signal in GOP units, the first GOP of the second image signal is encoded as a closed type that is encoded independently of the preceding GOP or depending on the preceding GOP. A first step of judging which type of open type is used, and a case where the first GOP of the second image signal is open type, the first inter-frame prediction coded image of the second image signal. A second step of replacing the group with an inter-frame predictive coding group based only on the first intra-coded image of the second image signal; and By providing the third step of transmitting the image signal following the first image signal, the first and second image signals can be GOP-converted without deteriorating the image quality and without generating noise at the corners. An image signal transmission method that can be switched and transmitted at an arbitrary timing in units can be realized.

[Brief description of the drawings]

FIG. 1 is a schematic diagram for explaining the principle of the present invention.

FIG. 2 is a schematic diagram for explaining a multiplexing process of an image signal in MPEG1.

FIG. 3 is a table showing the classification of MB types of B pictures.

FIG. 4 is a block diagram showing a configuration of a television broadcasting system according to the embodiment.

FIG. 5 is a flowchart showing an image stream switching processing procedure.

FIG. 6 is a block diagram showing a configuration of a conventional television broadcasting system.

FIG. 7 is a schematic diagram for explaining a sequence of images at the time of encoding and decoding of an image based on the MPEG standard.

FIG. 8 is a schematic diagram for explaining an open GOP and a closed GOP;

FIG. 9 is a schematic diagram for explaining a conventional problem.

[Explanation of symbols]

1, 10 ... television broadcasting system, 2, 11 ...
Image signal sending device, 3 ... MPEG encoder, 4 ...
Data storage unit, 5, 7, 13A, 13B ... Temporary data storage unit, 6, 14A, 14B, 15 ... Switch, 8 ...
... MPEG decoder, 12 ... Control unit, 16A, 16B
...... picture group substituted unit, 17A, 17B ...... MB code conversion unit, 18A, 18B ...... picture type and the number detecting _{unit, ST 1, ST 2, ST} 2 ', ST 3 ...... image stream.

Claims (2)

[Claims] 1. A plurality of encoded image groups leading an intra-frame encoded image are defined as a GOP (group of pictures).
The first and second GOPs comprising one or more GOPs
In the image signal transmitting apparatus for switching and transmitting the image signal in GOP units, the first GOP of the second image signal is replaced with the preceding GOP.
Determining whether the type is a closed type independently coded or an open type coded depending on a preceding GOP; and a first inter-frame prediction code of the second image signal. Means for replacing a group of coded images with a group of inter-frame predictive coding based only on the first intra-coded image of the second image signal, and the second image based on the determination result of the determining means When the first GOP of the signal is the open type, the second GOP replaced by the image replacing means is used.
Sending means for sending the image signal following the first image signal. 2. A plurality of coded image groups starting from an intra-frame coded image are defined as a GOP (Group of Pictures).
The first and second GOPs comprising one or more GOPs
In the image signal transmitting method of switching and transmitting the image signal in GOP units, the first GOP of the second image signal is set to the preceding GOP.
A first step of determining whether the type is a closed type independently encoded or an open type encoded depending on the preceding GOP; and the first GOP of the second image signal is In the case of the open type, the first inter-frame predictive coded image group of the second image signal is converted to the inter-frame predictive coded group based only on the first intra-frame coded image of the second image signal. And a third step of transmitting the replaced second image signal after the first image signal.